A technique has conventionally been present to generate an assembly sequence of a product from the computer aided design (CAD) data thereof. For example, a technique is present to generate an assembly sequence of a product using assembly constraint information that constrains adjacency relations among the parts forming an assembly model and position relations thereamong. According to another technique, evaluation factors are read from a database. The evaluation factors correspond to part properties of parts that form a product from three-dimensional data and work contents therefor; and image data of the parts are edited using colors that correspond to the evaluation scores corresponding to difficulty of assembling and disassembling related to the parts. Another technique is present to generate quantitative assembly data based on assembly information based on a shape model of a designed product. According to another technique, assembly and disassembly simulations are executed based on product design information and assembly and disassembly information; and evaluation is executed for assembly and disassembly properties. According to yet another technique, a part currently disassembled in the state where a product is midway in disassembling thereof is moved by a distance to be moved next that corresponds to the most closest distance between the currently disassembled part and the remaining parts at the present time point during the disassembling; and determination is made for each of the most closest distance and occurrence of an interference for the state after the currently disassembled part is moved (see, e.g., Japanese Laid-Open Patent Publication Nos. 2008-46924, 2005-275945, 2001-353631, H7-311792, and H10-312208).
However, according to the conventional techniques, when the assembly sequence of a product is determined by a user, to change the position of a part in the assembly sequence, the user performs multiple operations and in making a single change, a drag and drop operation and a cut and paste operation are performed. Thus, the user performs numerous operations.